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Biomechanics

Able to achieve relatively high level of function after STJ fusion

- previously believed that isolated STJ fusion should not be performed

- believed that triple arthrodesis was operation of choice for hindfoot

- STJ fusion has superior result with less stress on AJ

Average loss of DF 30% / PF 10%

Position of hindfoot determines flexibility of transverse tarsal (CCJ & TNJ) joints

- imperative that fusion be positioned in ~ 5^o valgus 

Anatomy

Largest and most powerful rotator cuff

- arises coastal border of scapula

- superior 2/3 tendon inserts into LT

- inferior 1/3 inserts into proximal humerus

Action

- IR (with T major, P major, Lat Dorsi)

- part of force couplet depressing humeral head

Incidence